io_uring/net: fix must_hold annotation

Fix up the io_alloc_notif()'s __must_hold as we don't have a ctx
argument there but should get it from the slot instead.
Reported-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/cbb0a920f18e0aed590bf58300af817b9befb8a3.1661342812.git.asml.silence@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/notif.c

@@ -73,7 +73,7 @@ struct io_kiocb *io_alloc_notif(struct io_ring_ctx *ctx,
 }
 
 void io_notif_slot_flush(struct io_notif_slot *slot)
-	__must_hold(&ctx->uring_lock)
+	__must_hold(&slot->notif->ctx->uring_lock)
 {
 	struct io_kiocb *notif = slot->notif;
 	struct io_notif_data *nd = io_notif_to_data(notif);